Patch "namei: ->d_inode of a pinned dentry is stable only for positives" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

    namei: ->d_inode of a pinned dentry is stable only for positives

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
namei-d_inode-of-a-pinned-dentry-is-stable-only-for-positives.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Al Viro <[email protected]>
Date: Sat, 27 Feb 2016 19:23:16 -0500
Subject: namei: ->d_inode of a pinned dentry is stable only for positives

From: Al Viro <[email protected]>

commit d4565649b6d6923369112758212b851adc407f0c upstream.

both do_last() and walk_component() risk picking a NULL inode out of dentry about to become positive, *then* checking its flags and seeing that it's not negative anymore and using (already stale by then) value they'd fetched earlier. Usually ends up oopsing soon after that...

---
 fs/namei.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -1742,11 +1742,11 @@ static int walk_component(struct nameida
 		if (err < 0)
 			return err;
 
-		inode = d_backing_inode(path.dentry);
 		seq = 0;	/* we are already out of RCU mode */
 		err = -ENOENT;
 		if (d_is_negative(path.dentry))
 			goto out_path_put;
+		inode = d_backing_inode(path.dentry);
 	}
 
 	if (flags & WALK_PUT)

@@ -3130,12 +3130,12 @@ retry_lookup:
 		return error;
 
 	BUG_ON(nd->flags & LOOKUP_RCU);
-	inode = d_backing_inode(path.dentry);
 	seq = 0;	/* out of RCU mode, so the value doesn't matter */
 	if (unlikely(d_is_negative(path.dentry))) {
 		path_to_nameidata(&path, nd);
 		return -ENOENT;
 	}
+	inode = d_backing_inode(path.dentry);
 finish_lookup:
 	if (nd->depth)
 		put_link(nd);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/bcache-fix-a-leak-in-bch_cached_dev_run.patch queue-4.4/locks-fix-unlock-when-fcntl_setlk-races-with-a-close.patch queue-4.4/namei-d_inode-of-a-pinned-dentry-is-stable-only-for-positives.patch queue-4.4/uml-fix-hostfs-mknod.patch